This invention relates generally to techniques for generating electromagnetic (photon) radiation that is modulated in energy relative to wave intensity. The term duality modulation is applied here to specify this form of modulation. In particular, the invention relates to applications of such duality modulated electromagnetic radiation in which it would be highly desirable to modulate the radiation with information, where that radiation simultaneously is highly depleted in its relative proportion of energy. For example, it is well known in the art that photon beams may be used to scan and characterize a target object that is potentially damaged by excessive absorption of energy. Alternatively, in other particular applications it may be desirable to minimize the target object's capability to conventionally detect an interrogating scan beam. In various communications applications, the objective may be to securely transmit a signal beam without incurring interception and detection by conventional receivers. All of these applications would benefit from the use of beams highly depleted in energy relative to wave intensity. Other applications make use of radiation having an energy component that is enriched relative to wave intensity.
In their U.S. Pat. No. 7,262,914 entitled “Method and Apparatus for Generating and Detecting Duality Modulated Electromagnetic Radiation,” the present inventors disclosed and claimed various embodiments of an invention that meets the goals outlined above. The disclosure of U.S. Pat. No. 7,262,914 is hereby incorporated by reference into this specification. Two of the inventors' earlier patents are also hereby incorporated by reference into this specification. These are U.S. Pat. No. 6,028,686. “Energy-Depleted Radiation Apparatus and Method,” and U.S. Pat. No. 6,804,470, also entitled “Energy-Depleted Radiation Apparatus and Method.”
In brief, all of the various forms of apparatus and corresponding methods that were claimed in U.S. Pat. No. 7,262,914 involved the convergence of a plurality of mutually coherent beams to form a periodic interference pattern. When a diffraction grating with a periodicity related to that of the interference pattern is positioned appropriately in the converging beams, the grating outputs a plurality of divergent duality-modulated beams. Although this arrangement operates satisfactorily in the manner described in the patent, a practical limitation is the inherent difficulty in aligning multiple beams appropriately to impinge on the grating. The present invention obviates this difficulty by avoiding the requirement for multiple beams, as further explained in the following summary.